MEMBRANE SEPARATION PROCESSES IN THE PULP AND PAPER-INDUSTRY

A study has been made on the utilization of inorganic membranes for the removal of colour from effluents of the first caustic extraction in the pulp and paper production. Experiments have been performed for ultrafiltration alone and, for this operation, in series with a microfiltration pretreatment. In both operations CARBOSEP tubular membranes were used with a microfiltration membrane of pore diameter equal to 0.14-mu and an ultrafiltration membrane with a cut-off of 10,000. The pressure ranged from one to five bar and feed circulation velocities of 0.7, 1.3 and 1.8 m/s were investigated. The introduction of microfiltration brings about no significant improvement of the quality and quantity of the permeates.